Process of starting induction-motors.



No. 7l4,824. Patntad Dec; 2, I902,

, A. SCHWARTZ.

PROCESS OF STARTING INDUCTION MOTORS.

(Application filed Mar. 18, 1901.) I (No Model.) I

I THE NGRRIS PETERS cmmwmuwmmsmsmm, my C UNITED STATES PATENT OFFICE.

ALFRED SCHWARTZ, OF COLOGNE, GERMANY, ASSIGNOR TO HELIOS ELEC- TRICALCONSTRUCTION COMPANY, OF COLOGNE-EHRENFELD, GERMANY.

PROCESS OF STARTING INDUCTION-MOTORS.

SPECIFICATION forming part of Letters Patent No. 714,824, dated December2. 1902- Applioation filed March 18, 1901. Serial No. 51,734- (Nomodel.)

To all whom it may cnocrn:'

Be it known that I, ALFRED SCHWARTZ, a subject of the German Emperor,and a resident of Cologne, Germany, have invented certain new and usefulImprovements in Processes of Starting Induction-Motors, of which thefollowing is a specification.

My present invention provides an improved process of startinginduction-motors, where- IO by also single-phased motors may be startedby utilizing an automatic clutch or coupling and whereby thestarting-current in motors for single-phased or multiphased currents maybe greatly reduced, so that larger types I5 of motors may be constructedwith short-circuit armatures than has been heretofore possible withrespect to the high starting-current. Moreover, the new method enablesspecial devices for displacing the phases in the auxiliary phaseemployed in asynchronous single-phascd motors to be omitted. In somecases the auxiliary phase may be dispensed with.

The principle involved by the invention is as follows: The shaft of thearmature is extended on either side and journaled so that the armaturemay be easily shifted in axial directions. When the armature having, forinstance, a short-circuit winding is located 0 in its stator field-coiland when inserted into the circuit, the armature will be pushed axiallyout from the field, and in this position,

in which it is partially out of the field, it will be started withoutcharge after a slight rotation is imparted to it either by hand orotherwise, said armature making its normal number of revolutions after ashort time. XVhen the same rotates at its normal speed, just at themoment of synchronism it is again pulled into the field and then coupledby means of a clutch also operated at this moment by the axial movementof the shaft. By reason of said clutch the motorfor instance,asingle-phased motor-will be coupled to its charge only after thesynchronism is reached. Experiments have proved that the starting of themotor under charge in this manner is effected in a few seconds.

The above method will now be clearly described with reference to theaccompanying drawings.

Figure 1 is a central longitudinal sectional view of a motor, thecasing, the pulley, and clutch-disk,and disengaging device and showingthe armature partially out of the casing. Fig. 2 is a rear elevation ofthe clutch-disk. Fig. 3 is a front elevation of the disengaging device,partly broken away.

The repelling force between the field-magnets Gr, Fig. 1, and thearmature K, which in Fig. l is shown shifted laterally, so as to bringthe armature outside the field, is produced by the fact that by reasonof the action of lines of force of said field high-potential currentswill be induced in the windings of the armature, the repelling force ofsaid currents being considerably stronger than the attractive force ofthe magnetism induced in the iron core of the armature. On the otherhand, when the armature occupies said position outside the field beforethe starting and when it is then inserted into the field said armaturewill certainly remain in said position for the reason stated. In thisposition a polyphase currentmotor will be started by itself, while asingle-phase currentmotor requires but a slight push in the direction ofits rotation. It is well known that a single-phase motor, the armatureof which is in its normal position, cannot be started even when a slightrotation is imparted to it, as the reaction produced by the induced cur-.rents in the armature is too strong'and as the action of the field istoo greatly reduced for this reason. When the armature is in theposition outside the field, which position will be termed startingposition, it will be seen that the currents in the armature areconsiderably weaker, as a portion only of thewindingsisinfiuencedbyinduction. Thereforethe 9o reaction of thearmature is also weaker and a slight push against the armature will besufficient to start the motor, which will rotate at the normal speedafter a short time. Then when the motor works nearly synchro- 5 nouslythe currents induced in the armature will be nearly zero and themagnetic attractive force on the iron core will be superior, whereby thearmature is drawn to the normal operative position. The arrangement thatthe armature in its starting position is partially out of the fieldserves the same purpose IOU as the insertion of a resistance into thearmature. However, it will be seen that in my improved construction anymaterial resistance will be dispensed with.

In order to automaticallyimpart the slight starting rotation to thearmature of singlephased motors, I utilize the well known method of producing by the combination with the main winding H, Fig. l, of anauxiliary winding A, an operative field starting the armature and givingthe same the normal speed. In order to enable a field of this kind to beproduced by means of the auxiliary winding A, both windings must bedisplaced with respect to each other, and, moreover, in the winding Amust be produced a current displaced in its phase with respect to thecurrent in the main winding. Heretofore this result has been attained byinserting induction-coils, condensers, or other similar devices. I haveprovided a much simpler method for attaining the desired result. Thecharacteristic feature thereof is that the winding A, which is connectedto the circuit, is extended on one side beyond the main winding H in theaxial direction, so that the winding completely or almost completelysurrounds the armature when the latter is in its starting position. Thecoils H are directly connected with the diaphragm tension, while thecoils A are arranged parallel to the main winding, as shown in Fig. 1.By reason of the fact that the number of windings in the starting-coil Awith respect to the number of windings in the main coil H, and thereforethe self-induction, is reduced and that by selecting a suitable materialof small conductivity the ohm resistance is increased I already obtain adisplacement of the phases of the currents in the main and auxiliarywindings; but this would not be sufficient to produce the above-namedstarting-field. The extension of the auxiliary winding beyond the mainwinding produces a further displacement of the phases of said currents,as it will be noted that the starting-coil A by reason of its forwardposition induces the entire winding of the armature K, while the maincoil H influences but a portion of said armature. Now when the relationbetween the induction-motor and a transformer is considered the armatureis to be considered as a short-circuit secondary coil of a transformer,while the starting-coil is equivalent to the primary coil of atransformer. Thus it will be seen that an increase of the watt componentof the current in the winding A with respect to the same component inthe Winding II, and therefore a further displacement of the phasesbetween the currents in both coils, will be obtained. Said displacementmay still be increased by arranging adjacent to the armature K on theshaft WV of the latter a wound or plain iron body S, which may belamellated or solid, so that it fills partially or completely the spaceleft in the field by the armature K when the latter is in its startingposition. Said body S immediately reinforces the field and increases,therefore, the self-induction in the inducing windings. This increasehas a higher effect in the main coil I-I than in the starting-coil A byreason of the greater number of windings in the former. Thestartingfield thus produced will be sufficient to start thesingle-phased motor in a very short time. The iron body S has a furtheradvantage for induction-motors. By reason of the increase ofself-induction in the windings it reduces considerably thestarting-current and permits, therefore, of a further application of theshort-circuit armature. When said body is provided with windings, it maybe employed as an auxiliary armature, reinforcing the starting-field andreducing the time of starting. Moreover, its magnetic resistance maythereby be modified. Then when the single-phased motor runs at itsnormal speed the starting-coil be cut out. This is automaticallyeffected by the axial movement of the armature produced at this moment.To this end I may employ, for instance, thedevicehereinafterdescribed.The two starting binding-posts a and a are connected to the mainbinding-posts a a so that they lie parallel to the main windings H ofthe motor. The clamps a and a are arranged parallel to the main windingH for the purpose of enabling the coils A to be disengaged independentof the main winding. (See Fig. 1.) The wire connects the binding-post ato a spring F, insulated on the frame of the motor-for instance, on thebearing thereofand sliding on the shaft, whereby it is electricallyconnected to the wire Z secured but not insulated on the bearing. Zleads to the starting-coil A, connected in turn by the wire i to thesecond binding-post a Thus the circuit of the starting-coil will beclosed when the armature is in its starting position. hen the armatureis brought to the operative position, the spring F will come to therecess E, and thereby open the circuit, as it no longer engages theshaft /V. When the armature is again brought to its starting position,the spring F is again brought into contact with the shaft, whereby themotor is prepared for the next starting. By reason of the lateralshifting imparted to the armature of an induction motor at the moment itreaches the normal speed the centrifugal clutch (shown in Fig. 2) willbe engaged. The motor is therefore able to attract the full charge inthe best manner when it has reached its maximum number of revolutions,the arrangement being such that the coupling is effected at that momentonly. In order to secure the engagement and disengagement of the clutchjust at the moment the motor runs at its full speed, I provide on thelaterallymovable driving part of the clutch a special disconnectingdevice, whereby the coupling is only effected when the required numberof revolutions has been reached.

Loosely mounted on the journal Z is a belt pulley B, said journal beingmovable to the right in the bearing L, Fig. 1. The overlapping edge Nprevents the pulley from being moved to the left. The inner cylindricalwall 0 of the extended part of the pulley receives the engaging jaws B,guided in the perforated projections of the disk S and moved radiallytoward the shaft by the action of springs G. Each of the jaws carries onone side a small roller X, which is located under the curved rim T whenthe motor does not run at the required speed. The disk S is keyed on theshaft W, while T is adapted to slide longitudinally on the latter. Therelative rotation between Sand T is avoided by means of four bolts D,screwed in the part T and extending through holes 0 in the disk S. Thefree ends of said bolts are also provided with small rollers Y. Arrangedbetween T and the collar A, keyed on the shaft, is a coilspring F, whichserves to soften the shocks in coupling and uncoupling the pulley. Solong as the speed of the motor is under the normal full speed theclutch-disk will be disengaged from the belt-pulley R. Further more, thejawsB cannot be influenced by the centrifugal force, as the spring Itholds the curved rim T over the rollers X; but when the full speed isobtained and when the armature pulls the shaft toward the right the jawsB will partially enter the hollow cylinder C. At the same time the diskT is moved in the same direction by the spring F, said disk being pushedback at the moment the small rollerY engages the wall K of the pulley,whereby the disk S enters alone the cylinder O, as the rollers X are nowdisengaged from T. Thus the jaws B are influenced by the centrifugalforce,whereloya sudden coupling with radial pressure is produced. Whenthe motor is cut out, the armature will be moved to the right out of thefield, and the centrifugal force of the jaws will be quickly decreased,so that the springs G may move the same toward the shaft and that therollers X may again be brought under the retainer T.

Having fully described my invention, what I claim, and desire to secureby Letters Patent, is-- A process of starting induction n1ot0rs, whichconsists in pushing the armature out of the field when the field-coil isinserted in the circuit, imparting a slight rotation to said armaturewhereby the motor may be rotated at its normal speed, then bringing thearmature back into the field, and automatically operating a clutchdevice through the movement of the armature, substantially as described.

In testimony whereof I have hereunto set my hand in presence of twowitnesses.

ALFRED SOIHVARTZ.

Witnesses:

CHARLES LESIMPLE, KARL SCHMITT.

